<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .buju{
            height: 100vh;
            display: flex;
            flex-direction: column;
            flex-wrap: wrap;
        }
        header {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 50px;
            background-color: #4a78c2;
        }
        main{
            flex: 1;
            display: flex;
            width: 100%;
            background-color: aquamarine;
        }
        .m1{
            width: 20%;
            height: 100%;
            background-color: cadetblue;
        }

        .m2{
            width: 80%;
            height: 100%;
            background-color: coral;
        }
        footer{
            position: fixed;
            bottom:0;
            left: 0;
            width: 100%;
            height: 50px;
            background-color: orange;
        }
    </style>
</head>
<body>
<div class="buju">
    <header></header>
    <main>
        <div class="m1"></div>
        <div class="m2"></div>
    </main>
    <footer></footer>
</div>
</body>
</html>